Recently, advances have been occurred in the development of a projection type display device (LED projector) that uses a light emitting diode (LED) as a light source.
In the LED projector where high luminance is required, when luminance is approximately equal to that of a projector on which a halogen lamp is mounted, large current corresponding to the luminance must be supplied to the LED. This causes a great temperature increase in the area between the LED and the substrate on which the LED is mounted. Depending on the emission color of the LED, the electricity-to-light conversion efficiency of the LED is sensitive to temperature. Accordingly, when the temperature in the LED exceeds an ambient temperature (environmental temperature), there is a possibility that the luminance of the LED will be greatly reduced. In such a case, therefore, the LED must be cooled by using a cooling element such as a Peltier element.
When the LED is cooled by using the cooling element, it is desirable for the temperature of the cooling element to be lower than the ambient temperature. However, since this causes the occurrence of dew condensation, measures against this occurrence must be taken into consideration simultaneously with the use of the cooling element.
For example, Patent Literature 1 discloses a method for preventing the occurrence of dew condensation in a cooling device for an electronic device that includes a semiconductor light source including a LED. In this cooling device, a cooling object (LED) attached to the heat absorbing surface of the Peltier element is housed in a hermetically sealed space in which dry air is contained. By dissipating heat absorbed by the heat absorbing surface of the Peltier element from the heat dissipating surface of the Peltier element to the outside through a heat transfer component that defines the hermetically sealed space, the occurrence of dew condensation is prevented in the hermetically sealed space while the LED is simultaneously cooled.